distinct site of isotope incorporation into the 

 otolith was not discernible. Since the radioactive 

 mark was on the edge of the otoliths from these 

 early sampling periods, it was more difficult to 

 identify than the mark left on otoliths offish sac- 

 rificed later in the experiment. Distinct bands of 



silver grains, designating the site of isotope up- 

 take, were evident in all but four otoliths sampled 

 from day 4 through day 63 (Fig. 2). A less dense 

 background of grains spanned 7 to 10 bands 

 around the site of uptake; postinjection increment 

 counts were made from the site of densest grain 









f Jl ^A 



-^' 



^ ,- 



*.-*^ 



'1 



s* 



Figure 2. — Example of the silver grains produced by the autoradiograph of "^^Ca in the otolith of a 69 mm 

 juvenile black rockfish. Arrow indicates band of densest grains; for scale, arrow = 35 ixm. This photo is from 

 the anterodorsal region of the otolith. Note the clear increments present on the left side of the figure, represent- 

 ing the increments distal to the time-mark. 



829 



